Magnetic alloy



Dec. 11, 1928. 1,695,038

O.E.BUCKLEY MAGNETIC ALLOY Filed March6, 1925 1L an H 0.01 Gauss I000 zooo Tenfiion, pounds ;per square inch mm: wire/'6 500M251 l which, when Patented Dec. 11,1928.

' UNITED STATES res-5,038

PATENT OFF-ICE.

. v b V OLIVER E. BUCKLEY, OI MAPLEWOOD, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO WESTERN ELECTRQIC COMPANY, INCORPORATED, A 'CORPORA'ITON OF NE YORK.

MAGNETIC ALLOY.

Application filed mm. a, 1925. serial No. 13,501.

This invention relates to the production and use-of a new material or substance having certain desirable magnetic and electrical qualities the chief one of which ishigh permea- & bility, especially at low ma netizing forces,

which is relatively independent of mechanical stresses applied tothe material. This material isan alloy containing nickel and iron and properly heat treated to give it'the desired high permeability.

In the Patent Ila-1,586,884, issued June 1, 1926, to 'G. W. Elmen, there is disclosed a magnetic allo' consisting .in' its preferred proportions o 78%% nickel and 21 iron iven a specifiedheattreatment, has remarkafily high permeability at low magnetizing forces. It is also there disclosed that the .alloy should be guarded against undue stresses and strains after it has been heat treated to develop high permeability, as the permeability is somewhat affected by such stresses and strains.

and iron in which the nickel content is somewhat less'are evenrmor'e sensitive to strain. In the present application, which is a continuation in part of my application Serial- No. 697 ,534, filed March 7 1924, the chief object of the invention is the production ofan alloy having one or more of the desirable characteristics-of the alloy described in the above mentioned Elmen application'but one which is much less sensitive to strain. .Other scription.

In the, accompanying a set of curves showing the relationship between tension and permeabilityof various nickel-iron alloys, and Fig. 2 shows a section objects will appear from the following deof a submarine cable in which the improved' material is utilized for inductive loading.

When a study was made of the effects of tension upon nickel iron alloys having from 65% to 90% nickel and the rest iron and all .being given the same treatment to secure as great uniformity and freedom from internalstrain as possible, it was discovered that if the nickel content was less than 80% or thereabout, the. permeability increased with tension while if the nickel "constituted above 80% or thereabout, the permeability de creased with tension, but in the composition containing approximately 80% of nickel, the permeability was velgy nearly independent of the tension applie compositions of nickel and iron.

In the abovementioned patent to G. W. 1

Other" alloys of nickel drawings, Fig. 1 is Later investigation specification. The agompanying drawing is a series of curves showing the relation between permeabllity at a magnetlzing force of .01 gauss and applied tenslon for various Elmen and in the Patent No. 1,586,874, issued June 1,1926, to O. E.'Buckley, there are described many'uses for such nickeliron alloys, one of the principal uses being as'a loading material for increasing the inductance of signaling conductors and especially transoceanic submarine cables. The magnetizingforces set up by the signaling current in such a cable ordinarily varies from around two "tenths c. g. s. unit (gauss) at the sending end to about .001 gauss near the middle and to exceedingly small values at the receiving end. As fully set forth in theBuckley patent, the properties of these alloys in their preferred proportions peculiarly adapt them for use as loading material for, long submarine cables and it was in connection with such use that the research leading to this invention was undertaken. The loading is preferably placed upon the cable conductor in the form of a layer of helically wrapped tape or wire. Qne manner of doing this is disclosed in Patent No. 1,586,887, issued June 1, 1926, to

G. W. Elmn. The loaded conductor'is passed through an electric furnace which is maintained at a temperature of about 900 C., and, as it emergesfrom the furnace, is cooled at the proper rate to give the material high permeability at low magnetizing forcesof the order encountered in submarine signaling. It would be of advantage to heat treat the tape in a, manner to secure high permeability before applying it to the conductor were it not for the fact that wrapping the to relieve the conductor from strain. 1 This means is described and claimed in Patent No. 1,586,875, issued June 1, 1926, to O. E. Buckley. r J

ployed to equalize this pressure in a manner quartz container which was 960 'C. After being in the furnace With the idea in mind that by varying the composition of the nickel iron alloy a material might be found which wouldpossess as hi h permeability as that of the alloy hereto ore used and not be subject to the objections to that alloy resulting from its sensitiveness to strain, measurements were made on wires so arranged that their permeabilities could be measured while the material was under tension of any desired amount. The type of strain used was that resulting from simple tension on the material. This was chosen for the sake of simplicity in experimental procedure and interpretation of results. The wires tested constituted a 'grad ed series of nickel'iron alloys extending from nickel to nickel. The invention however is not limited to strains introduced by tensions.

The heat treatment given to the Wires was as follows: The samples were placed in a then evacuated and inserted in a furnace which was maintained at a temperature of approximately about ten minutes the container was removed and allowed to cool slowly to room tem erature before being opened. No attempt as made to obtain the highest possible permeability. These experiments disclosed the existence of a narrow range in the neighborhood of 80% to 83% nickel in which the change of permeability With tension is relativel small and on one side of which permeability increases with tension while on the other side it decreases. The results of the tests are shown in the curves of the drawing. Although the curves show a maximum tension of 2000 pounds per square inch, the tests were actually conducted up to tensions of about 10,000 pounds per square inch without causing any marked variation in the curve representing the behavior of 80% nickel and 20% iron. Data were obtained also on an alloy comprising 81% nickel and 19% iron for field strengths up to six gauss and though the permeability changes within this range in a manner similar to that of the preferred composition of the above-mentioned Patent No. 1,586,88 to G. W. Elmen, and shown for example in a paper b Arnold and Elrnen entitled Permalloy, ournal of Franklin Institute, May, 1923, no marked variations were produced in the shapes of the curves giving t e relation of permeability to tension at a fixed field strength. The permeability of the 80% nickel composition was around 4,000 at H=.01 gauss as shown in the drawing and the initial'permeability of this material was around 3800. It is interesting'also to note that although the effects of tension on the permeability of pure iron and pure nickel are comparatively less than for these alloys, the direction of the tension effect in alloys having more than 80% nickel is the of the 80% same as that in pure nickel and the behavior of chromium to increase the resistivity of the material or the addition of copper to alterits mechanical properties. The results of these tests indicate that the insensitivity of tlie 1material to strain is not materially affecte small percentages so long, as the proportion of nickel in the alloy remains approximately 80% of the combined nickel iron content.

The exact ratio of nickel to iron however,

the addition of other ingredients in to obtain this result depends somewhat upon the strength of field to which the material is to be subjected but will probably lie within the limits of 80% to 83% nickel and 20% to 17% iron. Thus, for example, with an alloy of 81% nickel and 19% effect of tension upon magnetization changes iron, the sign of the several times during the process of magnetically saturating the material, although the degree of sensitivity to. strain is very slight over the entire range.

The experiments in stronger fields showed also that at about that composition which possesses the least variation with tension of permeability in low fields, the coercive force and the area of the hysteresis loop were also least affected by tension. For alloys containing less than 80% of nickel, the effect of ten-- sion is to reduce the coercive force and the hysteresis loss per cycle. In the case of alloys containing more than 80% of nickel, the effect of tension is to increase the coercive force I and the hysteresis loss per cycle. It is understood in both cases that coercive force and the h steresis losses compared are those obtain same maximum induction.

The resistivity of theallo comprising 80% Inn from measurements carried to the nickel and 20% iron was ound to be about 16 x 10' ohms per cm." The other alloys tested showed a change in resistivity in the same direction as the chan e when tensions were applied. The resistivity nickel composition remained substantially constant,a pro erty which, while not so. important in genera as that of stabilization of permeability, since the resistivity is not so sensitive to strain, isnevertheless quite, important.

Fig. 2 shows a portion of a submarine cable inductively loaded with an alloy such as that just described. Such a cableis described at length in Buckley, referred to above. In this figure a central copperconductor 1 is surrounded in permeability the Patent No. 1,586,874 to O. E.

by, co strand er strands 2 making a composite conductor. Tapecomposed of the improved alloy is wound helically about the conductor 1 forming a layer 3 of inductive loading. This in turn is surrounded by gutta' percha insulation 4 and the usual armori'ng and protective covering 5 The new alloy is particularly well adapted for this use where ver high permeability is desired as it is found-t at the hi hest permeability is Obtained in practice i the alloy is. of the composition which is relatively insensitive to strain. By testing variouscom ositions of nickel-iron alloys by 'themse ves, apart from the conductor, it has been found thatthe highest initial permeability is. ob-

then-heat treated, it has tained by special heat treatment of a compo sition of 78 70 nickel and 21 iron. However, by testing tapes of the various compositions applied to a co per conductor and been found that the highest inductance for small currents and I therefore the highest actual permeability is obtained with .a composition in which the nickel content is 80% to 81% of the nickeliron content.- The reason for the latter composition giving better' results in the case of i the loadedconductor isthought to be its deep water to alloys, for example,

smaller sensitiveness to strain. In the cooling stage of the heat'treatment, there is a tendency for the nickel ironloading material toadhere to the copper conductor with the consequent introduction of mechanical strain. This fact is apt to be particularly pronounced if the loading material is'applied tightly to the conductor. The strain introduced by adhesion impairs the desired characteristics of the alloy of 7 8 nickel and 21 iron much more thanalloys of ,80%'

to 81%nickel and 20% to 19% iron which,

as has been pointed out above are relatively 1. .A nickel iron alloy comprising nickel .T and iron, the nickel being between 80% and' 83% of the total iron-nickel content, and hav- 66 ing higher permeability than iron at mag.- netizing .forces less than a few tenths of a c.g. s. unit. v u v 2. A magnet1'c alloy comprising materials having an electric or magnetlcproperty which varies in one direction in one of said matebinds and in the opposite direction in another of said materials under varying applied mechanical forces over a certain range, said-alloy cont-aining'said materials in the proper proportions sothat the effects of .such mepally nickel an chanical. forces are balanced, whereby the l property in uestion of the alloy may be substantiallyin ependent of applied mechanical forces'over the said range.

3. A magnetic composition mainly comprising nickel and iron with nickel pre dominating and which has been heat treated to have a permeability greater than that of iron at magnetizingforces of a few tenths of a gauss and. substantially independent of agplied mechanical forces up to the point w ere the elastic limit is reached.

4. A' magnetic alloy which has a permeability 'greater than that of iron at magnetizing forces of a few tenths of a gauss comprising fromabout 80% to 83% nickel i and the remaining portionchiefly iron, said permeability being more nearly independent of applied mechanical forces than when the nickel component is either increasedor re duced.

5. A magnetic alloy which has a higher permeability than .iron at magnetizing forces of a few tenths of a gauss or less comprising from about 80% to 83% nickel and the rest iron, said permeability being substantially independent of "tension .over a wide range.

6. A magnetic composition which has a higher permeabilitythan iron at magnetizing forces of a few tenths of agauss or less and high permeability at forces of the order of 1. auss comprising from about 80% to 83% nlckel and the rest iron, said permeability being substantially independent of tensions from zero to at least 5000 pounds per squareinch. r 7. An alloy, the greater part of which is reater than that of-iron at a magnetizing orce 1 of a few tenths of a gauss and a resisnickel and the rest chiefly iron and which has been heat treated to have a permeability tivity which is substantially independent of 1 applied mechanical forces over a wide range.

8. An alloy, the greater partof which is 11o been heat treated to have a permeability nickel and the rest chiefly iron which has rces of a-few tenths of a gauss and so that greater than that. of iron at magnetizing o the permeability and resistivity are nearly independent of applied mechanical forces over a widerange;

9. The combination with an electric conductor of magnetic material associated thei'ewith comprlsmgian alloy containing princiiron, the amouilt of nickel constitnting from 80% to 83% of.

P 'fl t the total nickel iron contents.

central conducting member having loading material associated therewith, said principal] 1.0. A signaling .conductor comprising-a l agnetic 1%, material consisting ofan alloy containing 1 nickel and iron in which the amount 0 nickel present is'froin 80% to 83% L of the total nickeliroli content.

'11. A method of prep. amag'iieticalloy-which has the characteristic of constant permeability independent of mechanical strain, which consists in combinin inalloy form a magnetic material in whic the per- 6 meabil ity normally increases in strain, with a magnetic material in which the permeability decreases in strain in such proportions as to cause the strain permeability characteristics of one element to balance the strain per- 10 meability characteristics of the other element. 12. A continuously loaded signaling conductor comprising a conducting member having associated therewith a magnetic loading material which consists mainly of nickel and iron, with nickel predominating and which has been heat treated before its association with said member to have a permea- -bility which is higher than that of iron and which is substantially unimpaired by the process of said association.

In witness whereof, I hereunto subscribe my name this 5thday of March, A. D., 1925.

OLIVER E. BUOKLEY. 

